The present invention relates to a cleaning composition, and more particularly to a cleaning composition suitable for removing letters or marks written by dry ink markers, oils, fats, greases and polar substances from surfaces of rubbers, plastics and metals, and for removing flux residues from printed-circuit boards.
1,1,2,2-Tetrachloro-1,2-difluoroethane (hereinafter referred to as "flon-112") which has hitherto been used in a cleaning composition, is non-flammable and of low toxicity, and has the feature of dissolving oils, fats or greases without attacking materials to be cleaned, e.g. polymeric materials such as rubbers and plastics, and metals. However, flon-112 has the disadvantages in that it solidifies on the surface of materials to be cleaned, when used alone at room temperature, because of having a high melting point, i.e. 26.degree. C., and an ability of removing polar substances such as glycols and inorganic salts that is insufficient.
1,1,2-Trichloro-1,2,2-trifluoroethane (hereinafter referred to as "flon-113") which is a compound analogous to flon-112 and has advantages similar to flon-112, has no defect related to solidification on the surface of materials to be cleaned, since its melting point is low, i.e. -35.degree. C. However, since flon-113 has a low boiling point, thus is volatile, the surface of materials to be cleaned is cooled in excess by vaporization and accordingly condensation of moisture is takes place easily on the surface. For instance, this may cause corrosion of metals, particularly active metals such as zinc, aluminum and magnesium, and alloys containing these metals. Also, flon-113 does not remove polar substances as well as flon-112.
It is effective to use flon-112 in combination with flon-113 for the purpose of preventing solidification of flon-112. Such a flon-112/flon-113 mixed solvent is non-flammable and of low toxicity, and has similar advantages to those obtained by the single use of flon-112 or flon-113 in that the mixed solvent dissolves oils, fats or greases without attacking materials to be cleaned such as metals and polymeric materials. However, the flon-112/flon-113 mixed solvent is insufficient in its ability of removing polar substances such as glycols and inorganic salts, flux, letters and marks written by dry ink markers, and rust preventive oils. Moreover, the defect inherent in flon-112 due to its solidification on the surface of materials to be cleaned is eliminated to some extent in the mixed solvent, but insufficiently because flon-113 evaporates faster than flon-112 to leave large amounts of flon-112.
It is an object of the present invention to provide a cleaning composition which is non-flammable and has an improved cleaning power.
A further object of the present invention is to provide a non-flammable cleaning composition which has an improved cleaning power, and moreover which does not cause flon-112 to remain on the surface of materials to be cleaned and does not cause condensation of moisture (moisture absorption) on the surface of materials to be cleaned.
These and other objects of the present invention will become apparent from the description hereinafter.